A conducted emission mitigation method for software-defined radios through vector signal cancellation

Recently, Software-Defined Radio (SDR) has gained great popularity owing to its attractive merits, such as flexible signals configuration in multiple channels. However, commercial SDR equipment also has large spurious emissions in the Transmitting (Tx) channel. This paper presents a cascaded model for the Conducted Emission (CE) properties of a general SDR platform, which captures all the key components with high precision. Based on a deeper understanding of the CE properties, a mitigation method is proposed for suppressing the spurious emissions of an SDR Tx channel. This method is based on an efficient vector signal cancellation scheme, in which multiple SDR channels are adopted to suppress the second- and third-order harmonic signals simultaneously. A hardware prototype with dual SDR channels is built and measured for verification. Experimental results show that the suppression level of the third-order harmonic signal is 24 dB on average in the frequency range of 100 MHz to 3000 MHz. The theoretic limit of the suppression level is related to the magnitude and phase errors, and the suppression level may be further improved by calibrating each SDR channel.